Introduction

Client access to upstream API services is typically controlled by the application and configuration of
Kong authentication plugins.

Generic authentication

The most common scenario is to require authentication and to not allow access for any unauthenticated request.
To achieve this any of the authentication plugins can be used. The generic scheme/flow of those plugins
works as follows:

Apply an auth plugin to an api, or globally (you cannot apply one on consumers)

Create a consumer entity

Provide the consumer with authentication credentials for the specific authentication method

Now whenever a request comes in Kong will check the provided credentials (depends on the auth type) and
it will either block the request if it cannot validate, or add consumer and credential details
in the headers and forward the request

The generic flow above does not always apply, for example when using external authentication like LDAP,
then there is no consumer to be identified, and only the credentials will be added in the forwarded headers.

Consumers

The easiest way to think about consumers is to map them one-on-one to users. Yet, to Kong this does not matter.
The core principle for consumers is that you can attach plugins to them, and hence customize request behaviour.
So you might have mobile apps, and define one consumer for each app, or version of it. Or have a consumer per
platform, e.g. an android consumer, an iOS consumer, etc.

It is an opaque concept to Kong and hence they are called “consumers” and not “users”.

Anonymous Access

Prior to Kong 0.10.x, a given API could be configured to allow only authenticated access (by applying an
auth plugin) or only anonymous access - it was not possible to have a given API allow some
users to be authenticated and others to access anonymously.

Kong 0.10.x adds the ability to configure a given API to allow both authenticated and anonymous access.
You might use this configuration to grant access to anonymous users with a low rate-limit, and grant access
to authenticated users with a higher rate limit.

To configure an API like this, you first apply your selected authentication plugin, then create a new
consumer to represent anonymous users, then configure your authentication plugin to allow anonymous
access. Here is an example, which assumes you have already configured an API named example-api:

Create an example API

Issue the following cURL request to create example-api which will use the
mockbin service to echo the request:

Create an anonymous consumer

Every request proxied by Kong must be associated with a consumer. You’ll now create a consumer
named anonymous_users (that Kong will utilize when proxying anonymous access) by issuing the
following request:

The config.anonymous=<consumer uuid> parameter instructs the key-auth plugin on this API to permit
anonymous access, and to associate such access with the consumer id we received in the previous step. It is
required that you provide a valid and pre-existing consumer id in this step - validity of the consumer id
is not currently checked when configuring anonymous access, and provisioninf of a consumer id that doesn’t already
exist will result in an incorrect configuration.

Check anonymous access

Confirm that your API now permits anonymous access by issuing the following request:

$ curl -i-X GET \--url http://localhost:8000/auth-sample

This is the same request you made in step #3, however this time the request should succeed, because you
enabled anonymous access in step #5.

The response (which is the request as Mockbin received it) should have these elements:

Multiple Authentication

Kong 0.10.x extends the ability to apply multiple authentication plugins for a given API, allowing
different clients to utilize different authentication methods to access a given API endpoint.

The behaviour of the auth plugins can be set to do either a logical AND, or a logical OR when evaluating
multiple authentication credentials. The key to the behaviour is the config.anonymous property.

config.anonymous not set
If this property is not set (empty) then the auth plugins will always perform authentication and return
a 40x response if not validated. This results in a logical AND when multiple auth plugins are being
invoked.

config.anonymous set to a valid consumer id
In this case the auth plugin will only perform authentication if it was not already authenticated. When
authentication fails, it will not return a 40x response, but set the anonymous consumer as the consumer. This
results in a logical OR + ‘anonymous access’ when multiple auth plugins are being invoked.

NOTE 1: Either all or none of the auth plugins must be configured for anonymous access. The behaviour is
undefined if they are mixed.

NOTE 2: When using the AND method, the last plugin executed will be the one setting the credentials
passed to the upstream service. With the OR method, it will be the first plugin that successfully authenticates
the consumer, or the last plugin that will set its configured anonymous consumer.

NOTE 3: When using the OAuth2 plugin in an AND fashion, then also the OAuth2 endpoints for requesting
tokens etc. will require authentication by the other configured auth plugins.

When multiple authentication plugins are enabled in an OR fashion on a given API, and it is desired that
anonymous access be forbidden, then the request-termination plugin should be
configured on the anonymous consumer. Failure to do so will allow unauthorized requests.